A survey of recent studies on trends and allocations of resources in the American family structure, supplemented by empirical data on family dynamics, may be a step toward clarifying the issue of which processes of family life consistently contribute to children's performances in school. Whether family characteristics or family use of time and activities are more important to achievement may best be shown through an economic human capital approach to the family-school relationship; such an approach to analyzing data on family structure accurately interprets the contribution of family life to learning. Based on 887 responses to a questionnaire seeking information on family time use and activities, the relative importance of the following six aspects of family characteristics for school achievement was assessed: (1) socioeconomic status, (2) family structure, (3) mother's characteristics and availability, (4) parental attitudes and expectations, (5) use of child's time, and (6) parent/child interactions. Responses were matched to school data on math and reading scales. Results show that for reading: none of the SES variables was significant; among the family structure variables, only the presence of a younger, preschool sibling was significant; mother's education, mother's occupation, and educational expectations were positively associated with achievement; 6 out of the 10 significant variables measured time use or parent/child interactions. For math, all significant variables related to time use and activities. Thus, measured by the economic model of family impacts, differences in the allocation of after-school time may be important factors in student achievement. (JW)